Discards is an important issue in fisheries around the world. The spatial management of discards ... more Discards is an important issue in fisheries around the world. The spatial management of discards has attracted interest as a potential tool for minimizing the unwanted catch. The aim of the present work was to identify areas with high quantities of bottom trawl discarded catch regarding species subjected to MCRS, in six areas of southern European waters (southern Portuguese waters, Catalan Sea, Ligurian and northern Tyrrhenian Seas, Strait of Sicily, eastern Ionian Sea, and Aegean Sea). Analyses were based on two types of data: (a) the undersized catch of species subjected to MCRS from bottom trawl surveys and (b) the actual discarded catch (including undersized and non-undersized individuals) of species subjected to MCRS from commercial bottom trawling. Geostatistical analysis techniques were applied to the first type of data and Generalized Additive Models using environmental variables were applied to the second one. Subsequently, areas that persistently presented high quantities of discarded catch (i.e., "iDC grounds") or undersized catch (i.e., "iUC grounds") were identified and mapped. The "iDC grounds"/"iUC grounds" were located either over the slope or within the continental shelf and over marine plateaus, largely depending on the main target species of each fishery. Next, the overlap of "iDC grounds"/"iUC grounds" with the existing Fisheries Restricted Areas (FRAs) and the proposed Marine Protected Areas (MPAs) was estimated aiming to explore how spatial closures could contribute to the reduction of bottom trawl discarded catch/undersized catch. Certain spatial closures were more effective in the Central Mediterranean and others to the Eastern Mediterranean. The overlapping of existing FRAs with "iDC grounds"/"iUC grounds" did not exceed 24 % in any study area, whereas proposed MPAs, like the CIESM Marine Peace Parks, reached up to 90 % for the same study area.
A landing obligation was formally implemented in the European Union (EU) for the first 2 time, as... more A landing obligation was formally implemented in the European Union (EU) for the first 2 time, as part of the recent reform of the EU Common Fisheries Policy (CFP). Given the 3 reasonable success of the landing obligation in some countries such as the Faroe Islands, Iceland 4 and Norway, this policy is seen as a viable approach to tackle the long-recognized discarding 5 problem in EU waters. However, there has been some debate on whether there is sufficient 6 evidence to support the feasibility of such a measure in the EU-CFP. The EU landing obligation 7 will implicitly include all small-scale fisheries (SSF) provided the species captured are subject to 8 catch limits or minimum sizes (in the case of the Mediterranean). SSF were included irrespective 9 of the fact that the discarding problem in the EU has been historically associated with medium-10 to large-scale fleets (in particular largely mixed species trawl fisheries). Additionally, past 11 experiences with a discard ban policy are still limited to specific countries and/or specific 12 fisheries. This paper examined the appropriateness and feasibility of the recently implemented 13 EU landing obligation in SSF. The effects in the long-term are unpredictable, but available 14 evidence suggests that in the short to medium-term a landing obligation is likely to bring more 15 negative social, economic and ecological impacts than benefits. 16
Fishing activities in mainland Portugal waters represent an important economic activity that supp... more Fishing activities in mainland Portugal waters represent an important economic activity that supplies the high fish demand of national consumers, ranked high globally with an average annual per capita consumption of approximately 60kg. The Portuguese domestic mainland fisheries are largely concentrated in near-shore waters, with sardine (Sardina pilchardus), horse mackerel (Trachurus mediterraneus Trachurus trachurus), chub mackerel (Scomber japonicus), hake (Merluccius merluccius) and octopus accounting for most of the landings. Although there have been studies on unreported catches, by-catch and discarding in different fisheries, this is the first study to provide an overall estimate of the total quantity of catches, including discards from 1950-2010 based on a fishery-by-fishery approach. Furthermore, to make comparative analyses of the catches and discards among the different fisheries, each fishery was assigned to one of the following sectors: industrial (large-scale commercial), artisanal (small-scale commercial), or subsistence and recreational (both small-scale noncommercial). Overall, reconstructed total catches amounted to just under 21.6 million t for 1950-2010, which is slightly more than 2 times the 10,592,310 t of landings officially reported by Portugal for the same time period. The industrial sector (15.4 million t) accounted for nearly 72% of total catches as estimated here, while the artisanal, recreational and subsistence sectors accounted for 6 million t (28%), 58,000 t (0.3%) and 54,000 t (0.3%) of the total catches, respectively. Discards contributed the most to unreported catches, accounting for 7.6 million t of total catches (i.e., 35%), while unreported landings amounted to around 2.9 million t (13%) over the 1950 to 2010 time period considered here.
Objetivos | Pretende-se desenhar e implementar uma rede de roteiros subaquáticos no Algarve, reco... more Objetivos | Pretende-se desenhar e implementar uma rede de roteiros subaquáticos no Algarve, recolhendo informação relativa à caracterização socioeconómica e demográfica dos visitantes, aos diversos aspetos considerados no design dos roteiros, ao potencial dos roteiros no incremento da consciencialização ambiental dos utilizadores e, finalmente, ao real potencial dos roteiros na dinamização da atividade de turismo subaquático sustentável na região.
Current fishing practices often do not allow adequate selection of species or sizes of fish, resu... more Current fishing practices often do not allow adequate selection of species or sizes of fish, resulting in unwanted catches, subsequently discarded, with the consequent negative effects on both marine communities and fisheries profitability. The cross-analysis of density patches of potential unwanted catches and distribution of fishing effort can support the identification of spatial-temporal hot-spots in which the fishing pressure should be reduced to limit the amount of discards. The MinouwApp represents a technological and methodological framework to bring different, and structurally complex, sources of georeferenced data together into a simple visual interface aiming to interactively explore temporal ranges and areas of interest. The objective is to improve the understanding of fisheries dynamics, including discards, thus contributing to the implementation of discard management plans in a context of participative, ecosystem-based fisheries management strategies.
La pesquería de jaiba de la Ciénaga Grande de Santa Marta está sometida a una fuerte presión sobr... more La pesquería de jaiba de la Ciénaga Grande de Santa Marta está sometida a una fuerte presión sobre los individuos inmaduros, lo que ha conllevado a su sobrepesca. Objetivo. Se determinaron la dimensión y la ubicación de ventanas de escape para facilitar la salida de individuos con tamaños no deseados. Materiales y métodos. Mediante videograbaciones se estudió el comportamiento y sitios de preferencia de la jaiba dentro de la nasa. El tamaño de las ventanas se estimó utilizando las relaciones morfométricas: ancho a la base de la espina lateral (ABEL) vs. longitud del caparazón y ABEL vs. altura del cuerpo. Para establecer diferencias estadísticas entre los tamaños capturados y entre la captura por unidad de esfuerzo (CPUE) de nasas, con o sin ventanas, se utilizó la prueba W de Mann-Whitney. Resultados. Las relaciones fueron explicadas mediante las relaciones lineales: Lc=0.5938*ABEL+0.3102 y Alt=0.3094*ABEL+0.2934. El ABEL correspondiente a la talla de madurez se estimó en 106 mm. S...
Highlights The implementation of the discards ban in South European fisheries is perceived by f... more Highlights The implementation of the discards ban in South European fisheries is perceived by fishers as difficult Accompanying measures to the European discards ban should provide incentives for compliance The European discards ban is not perceived by fishers as conducive to future sustainable fisheries The fishing industry in South European fisheries do not consider that commercial utilization of former discards will offset costs of landing former discards
Marine protected areas (MPAs) are a global conservation and management tool to enhance the resili... more Marine protected areas (MPAs) are a global conservation and management tool to enhance the resilience of linked social-ecological systems with the aim of conserving biodiversity and providing ecosystem services for sustainable use. However, MPAs implemented worldwide include a large variety of zoning and management schemes from single to multiple-zoning and from no-take to multiple-use areas. The current IUCN categorisation of MPAs is based on management objectives which many times have a significant mismatch to regulations causing a strong uncertainty when evaluating global MPAs effectiveness. A novel global classification system for MPAs based on regulations of uses as an alternative or complementing the current IUCN system of categories is presented. Scores for uses weighted by their potential impact on biodiversity were built. Each zone within a MPA was scored and an MPA index integrates the zone scores. This system classifies MPAs as well as each MPA zone individually, is globally applicable and unambiguously discriminates the impacts of uses.
Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were an... more Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to identify trends and explore the relationships between the response variables (annual landings of 12 species) and explanatory variables [sea surface temperature, rainfall, an upwelling index, Guadiana river (south-east Portugal) flow, the North Atlantic oscillation, the number of licensed fishing vessels and the number of commercial fishermen]. Landings were more highly correlated with nonlagged environmental variables and in particular with Guadiana river flow. Both techniques gave coherent results, with the most important trend being a steady decline over time. A DFA model with two explanatory variables (Guadiana river flow and number of fishermen) and three common trends (smoothing functions over time) gave good fits to 10 of the 12 species. Results of other models indicated that river flow is the more important explanatory variable in this model. Changes in the mean flow and discharge regime of the Guadiana river resulting from the construction of the Alqueva dam, completed in 2002, are therefore likely to have a significant and deleterious impact on Algarve fisheries landings.
The first Mares Conference on Marine Ecosystems Health and Conservation was a successful event or... more The first Mares Conference on Marine Ecosystems Health and Conservation was a successful event organized by the MARES doctoral programme bringing together over 150 researchers in Olhão, Portugal from November 17th to 21st 2014. The conference was opened by Prof. Dr. Hans-Otto Pörtner, whose keynote address focused on a sectoral analysis by the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5) on the impacts of climate change on the world’s oceans. The first session on “Future oceans” was opened with a talk by Dr. Frank Melzner highlighting the problems calcifying invertebrates face in the warmer, more acidic and hypoxic waters. Other presenters dealt with changing global diversity patterns, ocean acidification, and the loss the genetic diversity. The second session on “Natural resources” was opened by Dr. Rainer Froese, who focused on whether or not the oceans can feed humanity. This talk introduced other contributions in the session, dealing with fisherie...
Experimental fishing was conducted off the port of Quarteira (southern Portugal) from October 201... more Experimental fishing was conducted off the port of Quarteira (southern Portugal) from October 2016 to February 2017 using standard trammel nets and modified nets rigged with a guarding net. The commercial catches of trammel nets rigged with a guarding net were 46.1% and 38.0% less than those of the standard net in numbers and economic value. However, there were significantly fewer commercial discards in biomass in the modified trammel nets (68.2%) and by-catch abundance and biomass were also lower in the modified nets (41.8% and 17.3% less, respectively). For the two main fish by-catch species, the modified net caught 62.2% fewer longfin gurnards (C. obscurus) and 33.1% fewer greater weever (T. draco) than the standard nets. Timing the removal from the nets of the main by-catch and discards species revealed savings in time associated with the use of modified nets. However, net damage occurred twice as much as in the modified net, probably contributing to the reduced commercial catch...
Although the bivalve dredge used on the Algarve coast (southern Portugal) is highly selective for... more Although the bivalve dredge used on the Algarve coast (southern Portugal) is highly selective for the target species, in some periods of the year the bycatch can exceed the catch of the commercial species. The present study aimed to quantify the bycatch and discards, estimate damage and mortality, and propose management measures to minimize discards and mortality. A total of 15 fishing surveys (60 tows) were performed using two types of dredges (“DDredge” targeting Donax trunculus and “SDredge” targeting Spisula solida and Chamelea gallina). Of the 85257 individuals (392.4 kg) of 52 taxa that were caught, 73.4% belonged to the target species, 22.1% to commercially undersized target species and 4.5% to bycatch species. Bycatch rates were lower for SDredge (13.5% in number and 6.3% in weight) than for DDredge (46.0% in number and 32.9% in weight). Damage and mortality rates were also lower using SDredge (1.3% and 1.0% of the total catches, respectively) than using DDredge (4.0% and 2....
In Portugal it has been estimated that unreported catches represent one third of total catches. H... more In Portugal it has been estimated that unreported catches represent one third of total catches. Herein, information on landings and total unreported catches (discards) by commercial métier were disaggregated into high taxonomic detail using published scientific studies. Fish accounted for 93.5% (115493 t) of overall unreported catches per year, followed by cephalopods (2345 t, 1.9%) and crustaceans (1754 t, 1.4%). Sharks accounted for 1.3% of total unreported catches in weight (1638 t/y). Unreported taxa consisted mostly of the commercial landed fish species: Scomber colias, Boops boops, Trachurus picturatus, T. trachurus, Merluccius merluccius, Sardina pilchardus, Liza aurata and Micromesistius poutassou, which together accounted for 70% of the unreported discarded catches. The number of unreported/discarded species was highest in artisanal fisheries, followed by trawl and purse seine. In artisanal fisheries, L. aurata, S. colias, S. pilchardus, Trachinus draco and B. boops account...
Numerous studies over the last decades have focused on marine protected areas (MPAs) and their ef... more Numerous studies over the last decades have focused on marine protected areas (MPAs) and their effects on fish communities. However, there is a knowledge gap regarding how species that live associated with soft-substrates (e.g., sand, mud) respond to spatial protection. We analyzed abundance, biomass and total lengths of the soft-bottom fishes in a multiple-use MPA in the north-eastern Atlantic, the Luiz Saldanha Marine Park (Portugal), during and after the implementation of its management plan. Data were collected by experimental fishing in areas with three different levels of protection, during the implementation period and for three years after full implementation of the MPA. Univariate analysis detected significant biomass increases between the two periods. Fish assemblages were mainly structured by depth and substrate, followed by protection level. Community composition analyses revealed significant differences between protection levels and between the two periods. Species exhi...
The effects of two different slipping methods on the survival, physical and physiological respons... more The effects of two different slipping methods on the survival, physical and physiological response of sardines, Sardina pilchardus, captured in a purse-seine fishery were investigated in southern Portugal. Sardines were collected and transferred into holding tanks onboard a commercial fishing vessel after being captured, crowded and deliberately released using two slipping procedures: standard and modified. The standard slipping procedure aggregated fish at high densities and made them "roll over" the floatline, while the modified procedure aggregated the fish at moderate densities and enabled them to escape through an opening created by adding weights to the floatline. Both slipping methods were compared with minimally harmed non-slipped sardines (sardines collected from the loose pocket of the purse seine). Survival rates were monitored in captivity over 28 days using three replicates for each treatment. The estimated survival of sardines was 43.6% for the non-slipped fi...
Understanding the ecological role that artificial structures might play on nearshore fish assembl... more Understanding the ecological role that artificial structures might play on nearshore fish assemblages requires the collection of accurate and reliable data through efficient sampling techniques. In this work, differences in the composition and structure of fish assemblages between the inner and outer sides of three marinas located in the temperate northern-eastern Atlantic Ocean were tested using three complementary sampling techniques: underwater visual censuses (UVC), baited cameras (BCs) and fish traps (FTs). UVCs and BCs recorded a comparable number and relative abundance of species, which in turn were much greater than those recorded by FTs. This finding supports the use of UVCs and BCs over FTs for broad ecologically studies, especially when dealing with structurally complex habitats such as artificial structures. We found differences in fish assemblage structure between the inner and outer sides of marinas, independently of the sampling method. Four small-sized species (Simil...
Understanding changes in biodiversity requires the implementation of monitoring programs encompas... more Understanding changes in biodiversity requires the implementation of monitoring programs encompassing different dimensions of biodiversity through varying sampling techniques. In this work, fish assemblages associated with the "outer" and "inner" sides of four marinas, two at the Canary Islands and two at southern Portugal, were investigated using three complementary sampling techniques: underwater visual censuses (UVCs), baited cameras (BCs), and fish traps (FTs). We firstly investigated the complementarity of these sampling methods to describe species composition. Then, we investigated differences in taxonomic (TD), phylogenetic (PD) and functional diversity (FD) between sides of the marinas according to each sampling method. Finally, we explored the applicability/reproducibility of each sampling technique to characterize fish assemblages according to these metrics of diversity. UVCs and BCs provided complementary information, in terms of the number and abundan...
Transactions of the American Fisheries Society, 1987
We developed a method for the analysis of observed changes in catch rates of similar species or g... more We developed a method for the analysis of observed changes in catch rates of similar species or groups of fish from southeastern Asia and the northwestern Atlantic region. Aggregated time series of catches per standard tow from research vessel surveys were examined as Markov chain models after transition probability matrices were derived from them by quadratic programming. The matrices were projected to provide some insight about stability and changes in the multispecies assemblages. Results from these analyses generally support inferences previously made from the data and provide some additional information regarding stability.
Discards is an important issue in fisheries around the world. The spatial management of discards ... more Discards is an important issue in fisheries around the world. The spatial management of discards has attracted interest as a potential tool for minimizing the unwanted catch. The aim of the present work was to identify areas with high quantities of bottom trawl discarded catch regarding species subjected to MCRS, in six areas of southern European waters (southern Portuguese waters, Catalan Sea, Ligurian and northern Tyrrhenian Seas, Strait of Sicily, eastern Ionian Sea, and Aegean Sea). Analyses were based on two types of data: (a) the undersized catch of species subjected to MCRS from bottom trawl surveys and (b) the actual discarded catch (including undersized and non-undersized individuals) of species subjected to MCRS from commercial bottom trawling. Geostatistical analysis techniques were applied to the first type of data and Generalized Additive Models using environmental variables were applied to the second one. Subsequently, areas that persistently presented high quantities of discarded catch (i.e., "iDC grounds") or undersized catch (i.e., "iUC grounds") were identified and mapped. The "iDC grounds"/"iUC grounds" were located either over the slope or within the continental shelf and over marine plateaus, largely depending on the main target species of each fishery. Next, the overlap of "iDC grounds"/"iUC grounds" with the existing Fisheries Restricted Areas (FRAs) and the proposed Marine Protected Areas (MPAs) was estimated aiming to explore how spatial closures could contribute to the reduction of bottom trawl discarded catch/undersized catch. Certain spatial closures were more effective in the Central Mediterranean and others to the Eastern Mediterranean. The overlapping of existing FRAs with "iDC grounds"/"iUC grounds" did not exceed 24 % in any study area, whereas proposed MPAs, like the CIESM Marine Peace Parks, reached up to 90 % for the same study area.
A landing obligation was formally implemented in the European Union (EU) for the first 2 time, as... more A landing obligation was formally implemented in the European Union (EU) for the first 2 time, as part of the recent reform of the EU Common Fisheries Policy (CFP). Given the 3 reasonable success of the landing obligation in some countries such as the Faroe Islands, Iceland 4 and Norway, this policy is seen as a viable approach to tackle the long-recognized discarding 5 problem in EU waters. However, there has been some debate on whether there is sufficient 6 evidence to support the feasibility of such a measure in the EU-CFP. The EU landing obligation 7 will implicitly include all small-scale fisheries (SSF) provided the species captured are subject to 8 catch limits or minimum sizes (in the case of the Mediterranean). SSF were included irrespective 9 of the fact that the discarding problem in the EU has been historically associated with medium-10 to large-scale fleets (in particular largely mixed species trawl fisheries). Additionally, past 11 experiences with a discard ban policy are still limited to specific countries and/or specific 12 fisheries. This paper examined the appropriateness and feasibility of the recently implemented 13 EU landing obligation in SSF. The effects in the long-term are unpredictable, but available 14 evidence suggests that in the short to medium-term a landing obligation is likely to bring more 15 negative social, economic and ecological impacts than benefits. 16
Fishing activities in mainland Portugal waters represent an important economic activity that supp... more Fishing activities in mainland Portugal waters represent an important economic activity that supplies the high fish demand of national consumers, ranked high globally with an average annual per capita consumption of approximately 60kg. The Portuguese domestic mainland fisheries are largely concentrated in near-shore waters, with sardine (Sardina pilchardus), horse mackerel (Trachurus mediterraneus Trachurus trachurus), chub mackerel (Scomber japonicus), hake (Merluccius merluccius) and octopus accounting for most of the landings. Although there have been studies on unreported catches, by-catch and discarding in different fisheries, this is the first study to provide an overall estimate of the total quantity of catches, including discards from 1950-2010 based on a fishery-by-fishery approach. Furthermore, to make comparative analyses of the catches and discards among the different fisheries, each fishery was assigned to one of the following sectors: industrial (large-scale commercial), artisanal (small-scale commercial), or subsistence and recreational (both small-scale noncommercial). Overall, reconstructed total catches amounted to just under 21.6 million t for 1950-2010, which is slightly more than 2 times the 10,592,310 t of landings officially reported by Portugal for the same time period. The industrial sector (15.4 million t) accounted for nearly 72% of total catches as estimated here, while the artisanal, recreational and subsistence sectors accounted for 6 million t (28%), 58,000 t (0.3%) and 54,000 t (0.3%) of the total catches, respectively. Discards contributed the most to unreported catches, accounting for 7.6 million t of total catches (i.e., 35%), while unreported landings amounted to around 2.9 million t (13%) over the 1950 to 2010 time period considered here.
Objetivos | Pretende-se desenhar e implementar uma rede de roteiros subaquáticos no Algarve, reco... more Objetivos | Pretende-se desenhar e implementar uma rede de roteiros subaquáticos no Algarve, recolhendo informação relativa à caracterização socioeconómica e demográfica dos visitantes, aos diversos aspetos considerados no design dos roteiros, ao potencial dos roteiros no incremento da consciencialização ambiental dos utilizadores e, finalmente, ao real potencial dos roteiros na dinamização da atividade de turismo subaquático sustentável na região.
Current fishing practices often do not allow adequate selection of species or sizes of fish, resu... more Current fishing practices often do not allow adequate selection of species or sizes of fish, resulting in unwanted catches, subsequently discarded, with the consequent negative effects on both marine communities and fisheries profitability. The cross-analysis of density patches of potential unwanted catches and distribution of fishing effort can support the identification of spatial-temporal hot-spots in which the fishing pressure should be reduced to limit the amount of discards. The MinouwApp represents a technological and methodological framework to bring different, and structurally complex, sources of georeferenced data together into a simple visual interface aiming to interactively explore temporal ranges and areas of interest. The objective is to improve the understanding of fisheries dynamics, including discards, thus contributing to the implementation of discard management plans in a context of participative, ecosystem-based fisheries management strategies.
La pesquería de jaiba de la Ciénaga Grande de Santa Marta está sometida a una fuerte presión sobr... more La pesquería de jaiba de la Ciénaga Grande de Santa Marta está sometida a una fuerte presión sobre los individuos inmaduros, lo que ha conllevado a su sobrepesca. Objetivo. Se determinaron la dimensión y la ubicación de ventanas de escape para facilitar la salida de individuos con tamaños no deseados. Materiales y métodos. Mediante videograbaciones se estudió el comportamiento y sitios de preferencia de la jaiba dentro de la nasa. El tamaño de las ventanas se estimó utilizando las relaciones morfométricas: ancho a la base de la espina lateral (ABEL) vs. longitud del caparazón y ABEL vs. altura del cuerpo. Para establecer diferencias estadísticas entre los tamaños capturados y entre la captura por unidad de esfuerzo (CPUE) de nasas, con o sin ventanas, se utilizó la prueba W de Mann-Whitney. Resultados. Las relaciones fueron explicadas mediante las relaciones lineales: Lc=0.5938*ABEL+0.3102 y Alt=0.3094*ABEL+0.2934. El ABEL correspondiente a la talla de madurez se estimó en 106 mm. S...
Highlights The implementation of the discards ban in South European fisheries is perceived by f... more Highlights The implementation of the discards ban in South European fisheries is perceived by fishers as difficult Accompanying measures to the European discards ban should provide incentives for compliance The European discards ban is not perceived by fishers as conducive to future sustainable fisheries The fishing industry in South European fisheries do not consider that commercial utilization of former discards will offset costs of landing former discards
Marine protected areas (MPAs) are a global conservation and management tool to enhance the resili... more Marine protected areas (MPAs) are a global conservation and management tool to enhance the resilience of linked social-ecological systems with the aim of conserving biodiversity and providing ecosystem services for sustainable use. However, MPAs implemented worldwide include a large variety of zoning and management schemes from single to multiple-zoning and from no-take to multiple-use areas. The current IUCN categorisation of MPAs is based on management objectives which many times have a significant mismatch to regulations causing a strong uncertainty when evaluating global MPAs effectiveness. A novel global classification system for MPAs based on regulations of uses as an alternative or complementing the current IUCN system of categories is presented. Scores for uses weighted by their potential impact on biodiversity were built. Each zone within a MPA was scored and an MPA index integrates the zone scores. This system classifies MPAs as well as each MPA zone individually, is globally applicable and unambiguously discriminates the impacts of uses.
Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were an... more Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to identify trends and explore the relationships between the response variables (annual landings of 12 species) and explanatory variables [sea surface temperature, rainfall, an upwelling index, Guadiana river (south-east Portugal) flow, the North Atlantic oscillation, the number of licensed fishing vessels and the number of commercial fishermen]. Landings were more highly correlated with nonlagged environmental variables and in particular with Guadiana river flow. Both techniques gave coherent results, with the most important trend being a steady decline over time. A DFA model with two explanatory variables (Guadiana river flow and number of fishermen) and three common trends (smoothing functions over time) gave good fits to 10 of the 12 species. Results of other models indicated that river flow is the more important explanatory variable in this model. Changes in the mean flow and discharge regime of the Guadiana river resulting from the construction of the Alqueva dam, completed in 2002, are therefore likely to have a significant and deleterious impact on Algarve fisheries landings.
The first Mares Conference on Marine Ecosystems Health and Conservation was a successful event or... more The first Mares Conference on Marine Ecosystems Health and Conservation was a successful event organized by the MARES doctoral programme bringing together over 150 researchers in Olhão, Portugal from November 17th to 21st 2014. The conference was opened by Prof. Dr. Hans-Otto Pörtner, whose keynote address focused on a sectoral analysis by the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5) on the impacts of climate change on the world’s oceans. The first session on “Future oceans” was opened with a talk by Dr. Frank Melzner highlighting the problems calcifying invertebrates face in the warmer, more acidic and hypoxic waters. Other presenters dealt with changing global diversity patterns, ocean acidification, and the loss the genetic diversity. The second session on “Natural resources” was opened by Dr. Rainer Froese, who focused on whether or not the oceans can feed humanity. This talk introduced other contributions in the session, dealing with fisherie...
Experimental fishing was conducted off the port of Quarteira (southern Portugal) from October 201... more Experimental fishing was conducted off the port of Quarteira (southern Portugal) from October 2016 to February 2017 using standard trammel nets and modified nets rigged with a guarding net. The commercial catches of trammel nets rigged with a guarding net were 46.1% and 38.0% less than those of the standard net in numbers and economic value. However, there were significantly fewer commercial discards in biomass in the modified trammel nets (68.2%) and by-catch abundance and biomass were also lower in the modified nets (41.8% and 17.3% less, respectively). For the two main fish by-catch species, the modified net caught 62.2% fewer longfin gurnards (C. obscurus) and 33.1% fewer greater weever (T. draco) than the standard nets. Timing the removal from the nets of the main by-catch and discards species revealed savings in time associated with the use of modified nets. However, net damage occurred twice as much as in the modified net, probably contributing to the reduced commercial catch...
Although the bivalve dredge used on the Algarve coast (southern Portugal) is highly selective for... more Although the bivalve dredge used on the Algarve coast (southern Portugal) is highly selective for the target species, in some periods of the year the bycatch can exceed the catch of the commercial species. The present study aimed to quantify the bycatch and discards, estimate damage and mortality, and propose management measures to minimize discards and mortality. A total of 15 fishing surveys (60 tows) were performed using two types of dredges (“DDredge” targeting Donax trunculus and “SDredge” targeting Spisula solida and Chamelea gallina). Of the 85257 individuals (392.4 kg) of 52 taxa that were caught, 73.4% belonged to the target species, 22.1% to commercially undersized target species and 4.5% to bycatch species. Bycatch rates were lower for SDredge (13.5% in number and 6.3% in weight) than for DDredge (46.0% in number and 32.9% in weight). Damage and mortality rates were also lower using SDredge (1.3% and 1.0% of the total catches, respectively) than using DDredge (4.0% and 2....
In Portugal it has been estimated that unreported catches represent one third of total catches. H... more In Portugal it has been estimated that unreported catches represent one third of total catches. Herein, information on landings and total unreported catches (discards) by commercial métier were disaggregated into high taxonomic detail using published scientific studies. Fish accounted for 93.5% (115493 t) of overall unreported catches per year, followed by cephalopods (2345 t, 1.9%) and crustaceans (1754 t, 1.4%). Sharks accounted for 1.3% of total unreported catches in weight (1638 t/y). Unreported taxa consisted mostly of the commercial landed fish species: Scomber colias, Boops boops, Trachurus picturatus, T. trachurus, Merluccius merluccius, Sardina pilchardus, Liza aurata and Micromesistius poutassou, which together accounted for 70% of the unreported discarded catches. The number of unreported/discarded species was highest in artisanal fisheries, followed by trawl and purse seine. In artisanal fisheries, L. aurata, S. colias, S. pilchardus, Trachinus draco and B. boops account...
Numerous studies over the last decades have focused on marine protected areas (MPAs) and their ef... more Numerous studies over the last decades have focused on marine protected areas (MPAs) and their effects on fish communities. However, there is a knowledge gap regarding how species that live associated with soft-substrates (e.g., sand, mud) respond to spatial protection. We analyzed abundance, biomass and total lengths of the soft-bottom fishes in a multiple-use MPA in the north-eastern Atlantic, the Luiz Saldanha Marine Park (Portugal), during and after the implementation of its management plan. Data were collected by experimental fishing in areas with three different levels of protection, during the implementation period and for three years after full implementation of the MPA. Univariate analysis detected significant biomass increases between the two periods. Fish assemblages were mainly structured by depth and substrate, followed by protection level. Community composition analyses revealed significant differences between protection levels and between the two periods. Species exhi...
The effects of two different slipping methods on the survival, physical and physiological respons... more The effects of two different slipping methods on the survival, physical and physiological response of sardines, Sardina pilchardus, captured in a purse-seine fishery were investigated in southern Portugal. Sardines were collected and transferred into holding tanks onboard a commercial fishing vessel after being captured, crowded and deliberately released using two slipping procedures: standard and modified. The standard slipping procedure aggregated fish at high densities and made them "roll over" the floatline, while the modified procedure aggregated the fish at moderate densities and enabled them to escape through an opening created by adding weights to the floatline. Both slipping methods were compared with minimally harmed non-slipped sardines (sardines collected from the loose pocket of the purse seine). Survival rates were monitored in captivity over 28 days using three replicates for each treatment. The estimated survival of sardines was 43.6% for the non-slipped fi...
Understanding the ecological role that artificial structures might play on nearshore fish assembl... more Understanding the ecological role that artificial structures might play on nearshore fish assemblages requires the collection of accurate and reliable data through efficient sampling techniques. In this work, differences in the composition and structure of fish assemblages between the inner and outer sides of three marinas located in the temperate northern-eastern Atlantic Ocean were tested using three complementary sampling techniques: underwater visual censuses (UVC), baited cameras (BCs) and fish traps (FTs). UVCs and BCs recorded a comparable number and relative abundance of species, which in turn were much greater than those recorded by FTs. This finding supports the use of UVCs and BCs over FTs for broad ecologically studies, especially when dealing with structurally complex habitats such as artificial structures. We found differences in fish assemblage structure between the inner and outer sides of marinas, independently of the sampling method. Four small-sized species (Simil...
Understanding changes in biodiversity requires the implementation of monitoring programs encompas... more Understanding changes in biodiversity requires the implementation of monitoring programs encompassing different dimensions of biodiversity through varying sampling techniques. In this work, fish assemblages associated with the "outer" and "inner" sides of four marinas, two at the Canary Islands and two at southern Portugal, were investigated using three complementary sampling techniques: underwater visual censuses (UVCs), baited cameras (BCs), and fish traps (FTs). We firstly investigated the complementarity of these sampling methods to describe species composition. Then, we investigated differences in taxonomic (TD), phylogenetic (PD) and functional diversity (FD) between sides of the marinas according to each sampling method. Finally, we explored the applicability/reproducibility of each sampling technique to characterize fish assemblages according to these metrics of diversity. UVCs and BCs provided complementary information, in terms of the number and abundan...
Transactions of the American Fisheries Society, 1987
We developed a method for the analysis of observed changes in catch rates of similar species or g... more We developed a method for the analysis of observed changes in catch rates of similar species or groups of fish from southeastern Asia and the northwestern Atlantic region. Aggregated time series of catches per standard tow from research vessel surveys were examined as Markov chain models after transition probability matrices were derived from them by quadratic programming. The matrices were projected to provide some insight about stability and changes in the multispecies assemblages. Results from these analyses generally support inferences previously made from the data and provide some additional information regarding stability.
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Papers by Karim Erzini